Back EMF smoke in controll panel


Page 1 of 4 1234 LastLast
Results 1 to 12 of 48

Thread: Back EMF smoke in controll panel

  1. #1
    Registered
    Join Date
    May 2017
    Location
    United States
    Posts
    40
    Downloads
    0
    Uploads
    0

    Default Back EMF smoke in controll panel

    Using Kflop and Kanalog in control panel to drive stepper motors. 4 Stepper motors are rated 5.7 volts , 3.5 amps and 22 (mH). Using Gecko G210 drives. Gecko drive is rated for up to 80 volts. Gecko recommends power supply voltage should be no less than 4 times or no more than 25 times the motor’s rated voltage. I first started with regulated a 48 volt power supplies but the Gecko drive went into fault condition and it turned out to be back emf on slow down of motor.

    So I added the Gecko recommended Return Energy Dump circuit and added a diode, led and capacitor to the Gecko Return Energy Dump circuit so I could see when the Gecko Return Energy Dump circuit was shunting EMF and working. (see circuit below) It worked great and fixed my problem, when the stepper motor decelerated at a quick rate the Return Energy Dump circuit turned on and I could see the led light and slowly dim, it works great. Gecko states this circuit protects stepmotor and servomotor drives from damage during periods of energy return when operating near maximum rated voltage.

    After posting on this forum my problem I revcieved help to fix the problem and I received several recommendations to change the regulated power supplies to unregulated diode/cap power supply.

    I upgraded to an unregulated 70 VDC 800 watt power supply which is near maximum rated voltage of the Gecko G210 and installed the Gecko Return Energy Dump circuit, one on each of the 4 stepper motors.

    I am bench testing everything with the steppermotors c-clamped to a table with no mechanical load that would increase the back EMF.

    Ran the motors and the Gecko Return Energy Dump circuits worked fine then after running at different speed several times the Gecko Return Energy Dump circuits started burning up with clouds of smoke. I saw the LED's stayed lit telling me the TIP 147 transistor shorted out and the 33 ohm resistor was burning up because the shorted transistor kept power through the resistor.

    Gecko circuit

    Back EMF smoke in controll panel-return-energy-dump-jpg

    Circuit I added the diode, resistor, LED and capacitor

    Back EMF smoke in controll panel-img028-pdf


    I don't know if the back EMF voltage or current is now the problem with the higher voltage power supply, the TIP 147 transistor in the Gecko Return Energy Dump circuit is rated for 100 volts at 10 amps.

    Does anyone have a suggestion on a circuit design or a transistor to use in the Return Energy Dump circuit hat would handle the higher voltage and current of the back emf. I do want to stay with the higher voltage power supply.

    I am now afraid not to use a Return Energy Dump circuit for fear of burning up the Gecko drives, the cloud of smoke from the Return Energy Dump circuit raises my concern.

    Thanks Joseph

    Similar Threads:
    Attached Thumbnails Attached Thumbnails Back EMF smoke in controll panel-return-energy-dump-jpg   Back EMF smoke in controll panel-img028-pdf  


  2. #2
    Gold Member Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    1684
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    I don't see anything that pulls the base of Q1 low. I would think a pulldown resistor between the base and ground would be in order. Maybe 10K? Might require some experimenting to find the correct value.



  3. #3
    Registered
    Join Date
    May 2017
    Location
    United States
    Posts
    40
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    Quote Originally Posted by Jim Dawson View Post
    I don't see anything that pulls the base of Q1 low. I would think a pulldown resistor between the base and ground would be in order. Maybe 10K? Might require some experimenting to find the correct value.
    The circuit does work it is designed by Gecko drives, it works fine at 48 volts using a 48 VDC regulated power supply but when I upgraded to a 70 VDC unregulated power supply at the higher voltage Q1 shorts out and fries the 33 ohm resistor.



  4. #4
    Gold Member Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    1684
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    Changing from 48V to 70V proabaly requires a change of R2, you've increased the system voltage by about 1/3. Probably getting enough base current through R2 to switch Q1 on. R3 may also have to be changed to a higher value keep the dump current within the working range Q1.

    EDIT: I just looked at the data sheet on the TIP147, it has built in pull down resistors. So just changing the value of R2 should fix the problem.

    http://www.mouser.com/ds/2/149/TIP147T-890154.pdf



  5. #5
    Registered
    Join Date
    May 2017
    Location
    United States
    Posts
    40
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    The following is the circuit description from Gecko: CIRCUIT DESCRIPTION:

    Normally power supply current flows thru rectifier D1, biasing Q2 off via R2. If the direction of current reverses, D1 shuts off and a reverse voltage develops across R1. This voltage now turns Q1 on. The returned current now flows from the drive, thru Q1 and to ground via R3. The main purpose of R3 is to keep Q3 within its secondary-breakdown limits (SOA).

    I think Gecko meant to say Q1 instead of Q3 in the last sentence there is no Q3. Based on what you said and Gecko's circuit description I think your statement of " R3 may also have to be changed to a higher value keep the dump current within the working range Q1" may be what needs to be done not changing R2. I don't know how to calculate what I should change R3 to and buying and burning up resistor as trial and error is not a good way to do it.

    If I am trying to keep Q1 within its secondary breakdown limits, maybe it would be good to also change out Q1 to a more robust transistor but again I would need to have someone tell me what would be a better darlington transistor to use and the R3 resistor value and wattage to use for either the TIP147 or for an upgraded transistor that has a higher breakdown limit. Perhaps there is a transistor that a limit that can still use the same R3 resistor if that's the problem. One of the things I am concerned with is the TIP147 has a voltage rating of 100 volts and I would think the back EMF could easily exceed the voltage rating of the TIP147. The circuit worked at 48 volts if the back EMF doubles that voltage and its still below the TIP147 rating but double the 70 volts and its 40 volts above the TIP147 voltage rating. I don't know how much voltage Back EMF produces but the way the transistor shorted out I don't know if its a current issue, voltage issue or both.

    I need a recommendation on resistor value and if the TIP 147 is still viable at the higher voltage.

    Thanks Joseph

    Help please

    Joseph



  6. #6
    Registered john-100's Avatar
    Join Date
    Mar 2007
    Location
    uk
    Posts
    1415
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    looking at the modded current dump circuit

    when the returned energy rapidly increases the voltage across C1,
    normally the TIP147 transistor connects the 33 ohm resistor across the capacitor C1 to disipate the excess energy

    with the modification the second 1000uF & 1N4004 will effectively short circuit the 33 ohm resistor and
    result in a larger current flowing through the transistor that could be damaging it

    try adding a 10 ohm resistor in series with the 1N4004 diode to reduce the initial current that charges the added 1000uF capacitor

    Back EMF smoke in controll panel-energy-dump-3-jpg

    john



  7. #7
    Registered
    Join Date
    May 2017
    Location
    United States
    Posts
    40
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by john-100 View Post
    looking at the modded current dump circuit

    when the returned energy rapidly increases the voltage across C1,
    normally the TIP147 transistor connects the 33 ohm resistor across the capacitor C1 to disipate the excess energy

    with the modification the second 1000uF & 1N4004 will effectively short circuit the 33 ohm resistor and
    result in a larger current flowing through the transistor that could be damaging it

    try adding a 10 ohm resistor in series with the 1N4004 diode to reduce the initial current that charges the added 1000uF capacitor

    Back EMF smoke in controll panel-energy-dump-3-jpg

    john
    I understand your point. This will in effect be parralling the two resistors which would be raising the resistance through Q1 to ground instantaneously lowering the current.
    I am only looking to charge c2 to lite the LED with out c2 the LED only blinks quickly and that was when I tested it using the 48 vdc power supply. Now after your comments i think that 10 ohms may not be high enough to lower the initial current enough. How high of a resistor can i use and still charge c2 so that I minimize initial current on Q1 Do you think the TIP147 rated at 100 volts is ok for the higher 70 volt power supply?



  8. #8
    Registered john-100's Avatar
    Join Date
    Mar 2007
    Location
    uk
    Posts
    1415
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    when the TIP147 switches on ,
    the 33 ohm resistor will initially will be in parallel with the 10 ohm resistor , plus the effective series resistance of the capacitor and the forward resistance of the 1N4004 (this is about 10 ohms not the 7.7 ohms of the 33ohm and 10 ohm resistors in parallel)
    but rapidly increase to 33 ohm as the 1000uF capacitor (C2) is charged

    as the TIP147 will be switched on as soon as the voltage across the driver supply terminals is around 2 V higher than the power supply output
    I would expect the TIP collector at switch on will be about 7.5 A ( give or take a little , depending on the amount of returned energy )

    as the diode D1 isolates the power supply as soon as the drivers supply terminals are 0.7V higher
    the question is whats the off load voltage from your power supply ???
    if its 80V the maximum voltage across the TIP147 will be about 82V


    John



  9. #9
    Registered
    Join Date
    May 2017
    Location
    United States
    Posts
    40
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by john-100 View Post
    when the TIP147 switches on ,
    the 33 ohm resistor will initially will be in parallel with the 10 ohm resistor , plus the effective series resistance of the capacitor and the forward resistance of the 1N4004 (this is about 10 ohms not the 7.7 ohms of the 33ohm and 10 ohm resistors in parallel)
    but rapidly increase to 33 ohm as the 1000uF capacitor (C2) is charged

    as the TIP147 will be switched on as soon as the voltage across the driver supply terminals is around 2 V higher than the power supply output
    I would expect the TIP collector at switch on will be about 7.5 A ( give or take a little , depending on the amount of returned energy )

    as the diode D1 isolates the power supply as soon as the drivers supply terminals are 0.7V higher
    the question is whats the off load voltage from your power supply ???
    if its 80V the maximum voltage across the TIP147 will be about 82V


    John
    I have 6.8k 2 watt, 1k 1\2 watt and 150 ohm 1\2 watt resistors i would like to use what I have its Saturday I would like to use the 1k if you think it would work i have transistors and diodes so I can work on it now but if you think i need to use a 10 ohm I'll wait till I can get them, no radio shacks around here

    Last edited by mirocha; 08-12-2017 at 07:27 PM.


  10. #10
    Registered john-100's Avatar
    Join Date
    Mar 2007
    Location
    uk
    Posts
    1415
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    if you have them , three or four 150 ohm resistors you can wire in parallel to give you 40 to 50 ohms could work instead of the 10 ohm resistor

    alternatively , depending on the components you have , some thing like this could work if you have a 100V NPN transistor
    and 100uF 100V capacitor

    Back EMF smoke in controll panel-energy-dump-4-jpg
    or
    Back EMF smoke in controll panel-energy-dump-5-jpg

    John

    Last edited by john-100; 08-12-2017 at 07:46 PM. Reason: add energy dump 5 jpeg


  11. #11
    Registered
    Join Date
    May 2017
    Location
    United States
    Posts
    40
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    I replaced the diodes and transistor in one of the blown return energy dump circuits, I left out what I added the diode, cap, led and resistor to try the original gecko circuit and after multiple tries it seems to work but with out the led there is no indication Q1 is turning on, but nothing smoked.

    I will order the parts for your design of the circuit, one resistor you say to use a 22k to 100k resistor can you let me know which is best I will be ordering the parts so I may as well get what is best. Also for the NPN transistor I could get the complementary TIP 142 which is a NPN 100 volt rated, let me know which transistor I should order.

    Thank you so much you, I will post once I get the parts and test it out.


    Joseph



  12. #12
    Registered john-100's Avatar
    Join Date
    Mar 2007
    Location
    uk
    Posts
    1415
    Downloads
    0
    Uploads
    0

    Default Re: Back EMF smoke in controll panel

    as its midnight I'll have another look at it in the morning and post any more thoughts I have

    for the MPSA42 a base resistor any spare resistor between 22K & 100K should work
    but I would probibly go for 47K if I bought parts for the project

    John



Page 1 of 4 1234 LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Back EMF smoke in controll panel
Back EMF smoke in controll panel